<MRow Align="@AlignTypes.Center">
    <MCol>
        <MSelect @bind-Value="_value"
                 Items="items"
                 ItemText="u => u"
                 ItemValue="u => u"
                 Disabled
                 Label="Disabled"></MSelect>
    </MCol>
    <MCol>
        <MSelect @bind-Value="_value"
                 Items="items2"
                 ItemText="u => u.Key"
                 ItemValue="u => u.Key"
                 ItemDisabled="u => u.Value"
                 Label="Disabled Item"></MSelect>
    </MCol>
</MRow>

@code {
    List<string> items = new() { "Foo", "Bar", "Fizz", "Buzz" };
    string _value;

    List<KeyValuePair<string, bool>> items2 = new Dictionary<string, bool>
    {
        { "Foo", false },
        { "Bar", false },
        { "Fizz", true },
        { "Buzz", false }
    }.ToList();
}